If you have ever watched a version of Gundam SEED where the ending feels "longer" or includes a funeral, you have seen "Episode 51."
The term "Episode 51" is sometimes confused with the sequel series, Gundam SEED Destiny gundam seed 51
The producers cut two full "recap" episodes (episodes 14 and 26) to improve the pacing for modern viewing. What was added? If you have ever watched a version of